This invention relates to apparatus and methods for manufacturing intraocular lenses (IOLs). More particularly, the application relates to an apparatus for protecting the edge geometry of an IOL during the polishing process.
An intraocular lens is commonly used to replace the natural lens of a human eye when warranted by medical conditions. Often, an IOL is implanted in a region of the eye known as the capsular bag or posterior capsule.
One problem frequently associated with IOLs is the phenomenon of posterior capsule opacification (PCO), in which epithelial cells from the posterior capsule tend to grow in front of and/or behind the optic of the IOL. This tends to block the optic and to impair vision.
Another concern with IOLs is glare. Light tends to reflect off the edges of the IOL, which can annoy the patient. In some cases, edge glare can be so irritating that the IOL must be removed and replaced.
A new generation of IOLs has been developed to obviate the problems of PCO and edge glare. Specifically, the new IOLs have been provided with special edge configurations which inhibit the growth of epithelial cells around the lens and reduce the amount of light reflected toward the optical axis. Examples of such edge configurations are shown in U.S. Pat. No. 6,162,249 to Deacon et al, the disclosure of which in its entirety is hereby incorporated by reference.
The new-generation IOLs may be manufactured using any convenient technique. Typically, they are lathed from blanks of polymerized lens material, and then polished to a desired optical finish. A preferred polishing method involves tumbling a lens cryogenically in a vessel filled with glass beads and polishing fluid. During this process, the sharp posterior edge of the lens tends to become rounded and indistinct. One solution to this problem is to mask the edge during polishing, but no apparatus for efficiently and uniformly masking an IOL edge has been discovered until now.
It would be advantageous, therefore, to provide an apparatus and method for protecting the edge geometry of an IOL during polishing.
A method and apparatus for protecting the edge geometry of an IOL during polishing have been discovered. Specifically, the method comprises encasing a peripheral portion of an IOL in a protective device before placement in a polishing apparatus such as a tumbler.
The protective device comprises a solid body having a cavity for receiving the IOL, and a peripheral portion for surrounding and protecting the edge of the IOL. Preferably, the solid body is made of a relatively durable material, such as cast acrylic, which allows it to be used more than once before disposal.
In one embodiment of the invention, the solid body comprises an annulus having a constant inner diameter slightly less than the outer diameter of the IOL. Thus, the annulus receives the IOL in an interference fit.
In another embodiment of the invention, the solid body comprises an annulus having retaining members and a receiving portion. The retaining members include a first projection extending radially inwardly along the inner circumference of the annulus proximate the top surface and a second projection extending radially inwardly along the inner circumference of the annulus proximate the bottom surface. The receiving portion extends longitudinally between the top and bottom surfaces and has an inner diameter approximately equal to the outer diameter of the IOL. The IOL is captured between the first and second projections.
Each and every feature described herein, and each and every combination of two or more of such features, is included within the scope of the present invention provided that the features included in such a combination are not mutually inconsistent.